Method of production of fabric bags or containers using heat fused seams

ABSTRACT

A method of producing flexible polypropylene fabric bags with heat fused seams comprising providing fabric pieces, wherein each fabric piece has a coated side and an uncoated side; positioning fabric pieces so that a coated side of one fabric piece faces a coated side of another fabric piece; selecting an area of fabric to be joined for forming a seam or joint; applying heat to the area to be joined that is less than the melting point of the fabrics, for forming one or more seams or joints and wherein the heat fused seams or joints of a resulting polypropylene bag retains at least 85% of the fabric strength without using sewing machines.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division of U.S. patent application Ser. No. 16/126,635, filedon 10 Sep. 2018 (issued as U.S. Pat. No. 10,974,869 on 13 Apr. 2021),which is a continuation of U.S. patent application Ser. No. 14/297,441,filed on 5 Jun. 2014 (issued as U.S. Pat. No. 10,112,739 on 30 Oct.2018), which claims priority of U.S. Provisional Patent Application Ser.No. 61/831,476, filed on 5 Jun. 2013; U.S. Provisional PatentApplication Ser. No. 61/890,664, filed on 14 Oct. 2013; U.S. ProvisionalPatent Application Ser. No. 61/909,737, filed on 27 Nov. 2013, and U.S.Provisional Patent Application Ser. No. 61/994,642, filed on 16 May2014, each of which is hereby incorporated herein by reference.

U.S. patent application Ser. No. 14/297,331, filed on 5 Jun. 2014, ishereby incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable

REFERENCE TO A “MICROFICHE APPENDIX”

Not applicable

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to the bulk bag industry and the art forproduction of bulk bags without use of sewing machines and stitchedseams. The invention further relates to production of flexible fabricpackaging, bags or containers without thread contamination and minimalhuman contact with the interior of the packaging, fabric or container tohelp eliminate concerns regarding bacterial contamination. The inventionfurther relates to production of nearly air tight flexible fabricpackaging, bags or containers that do not contain stitching or sewingholes.

2. General Background of the Invention

Woven polypropylene fabrics have been the fabric of choice in certainindustries, including the bulk bag industry, given the strength, costand flexibility of the fabrics. Although woven polypropylene fabrics andsome similar fabrics are very strong, they are also very chemicallyinert. The polypropylene fabrics are highly oriented through a heatingand stretching process to achieve maximum strength while maintaining theneeded flexibility of fabrics to fit the needs of the marketplace. Dueto these properties, it is very difficult to find a method of connectingtwo polypropylene fabrics without damaging the fabric itself, therebyreducing notably the strength and usefulness of the fabrics.

The Bulk Bag Industry is now over 40 years old. The very first bulk bagswere constructed by combining various configurations of woven fabricsand woven webbing by sewing them together to get the needed strength.

Today, sewing remains nearly the exclusive method for connecting thematerials of construction when making bulk bags. The determination ofwhich fabrics to use and which sewing patterns and which threads to useto combine these parts to create the most economical bulk bag containerare well known and have been studied in great detail.

However, the basic methods cannot produce the most economical containeras the act of sewing reduces the fabric strength through the needlepunctures. The average sewn seam in these high strength wovenpolypropylene fabrics creates seams that are generally about 63% of thestrength of the unsewn fabrics.

Therefore, in order for the seams to be strong enough, the fabricsthemselves must be constructed thicker and stronger to make up for theloss of strength in the seam.

Many efforts have been made to find an acceptable alternative to sewingpolypropylene fabrics for several reasons.

1. The act of sewing creates thread ends that must be cut from the endof each sew line. These ends often get loose and can become unwantedcontamination within the bags.

2. Because of the high heat generated by the needles passing throughthis tough polypropylene fabric, threads are often breaking. This causesproduction to momentarily stop while the machine is re-threaded.

3. Sewing machines can run at speeds of several thousand stitches perminute. At this high speed with many mechanical parts, there is a highincidence of parts breakage and needle breakage which stops productionof that machine while it is repaired.

4. Because of points 2 & 3, the production of bulk bags, for example,requires a high amount of labor to operate these machines and deal withthese issues. Global bulk bag production has largely taken place outsidethe United States, to be produced in countries with abundant sources oflow wage labor.

Furthermore, even sewing seams reduce the strength of the polypropyleneor other similar fabrics as the needle punctures break the fibers in thearea and reduce the fabric total strength. The number of stitches ineach inch or centimeter of the seam, the needle size and the thicknessof the thread used to make the stitch, all play a part in the overallstrength of the resulting seam. Often these seams produce a joint thatis about 63 to 70% of the strength of the unstitched fabric. Due to theweakening of the fabrics, fabrics that are 30% stronger than would betheoretically needed to carry the very heavy weights that bulk bags aredesigned to carry may be used. For all of these reasons, an alternativeto sewing has been desired and sought after within the industry for manyyears.

Thus, for many years, this industry has searched for an alternative tosewing as a method of bulk bag construction. Various glues and variouswelding methods have been tried. Contact glues have been foundunsuccessful due to;

1. poor peeling strengths,

2. the lack of a permanent bond, (contact glues stay active so they canbe peeled and reattached over and over)

3. a bond that is easily affected by temperature changes (glue oftenmelts at very low temperatures and becomes inactive in coolertemperatures)

4. shear strength that is only attained with very large area typecoverage.

Solvent glues have also failed due to the following;

-   -   a. joints are brittle and inflexible    -   b. often involve hazardous elements not allowable in food        packaging and    -   c. fabric strength is reduced by molecular reconfiguration.

Heat welding has been tried and largely rejected because to heat weld asin the prior art, one must reach the melting point of the polypropylenefabrics to bond them together. However, the polypropylene fabrics arehighly oriented and bringing them up to this temperature level resultsin a fabric tensile strength loss of approximately 50%.

Laser welding has been tried and showed some marginal success but thismethod is not economically feasible due to low production rates and veryhigh capital costs.

The basic issue has always been that bulk bags must safely carrytremendous weights, for example in some cases up to 3,300 (1,497kilograms) or 4,400 pounds (1,996 kilograms). Many prior efforts haveshown that joints can be achieved but nothing in the prior art has shownitself to be able to carry the tremendous weights with the required 5 to1 lifting safety in the resulting containers.

Therefore, after 40 years of production, sewing still remains the basicmethod of producing bulk bags. Bulk bags are still manufactured largelythrough the original methods of sewing woven polypropylene fabricstogether to form the bag and its lifting components. As discussed above,polypropylene has been the primary fabric of choice due to itscombination of strength, flexibility, and cost.

The art of heat sealing is well known in plastic fabric industries suchas those industries using polyethylene or PVC fabrics. The prior artmethod has been simple. Heat the fabric up to something higher than themelting temperature of polyethylene than squeeze the fabrics partstogether with enough force to squeeze any melting laminated coatings outfrom between the fabrics and allow the fabrics to join directlytogether. Heat sealing equipment is useful in that it is significantlymore amenable to automation than sewing machines. It has far less movingparts and can be electronically supervised for dependable repeatability.

In the prior art, polyethylene fabrics are heated up past their meltingpoint, then squeezed together with sufficient pressure (for example, 20psi (137 kilopascal)) to be sure the fabrics meet and join for apre-determined amount of time, and the joint is made. This joint istypically around 80 to 85% of the original strength of the materials.Since these materials are not so highly oriented, as compared topolypropylene, this high heat method results in an acceptable joint. Inthe prior art, pressure may generally be applied at approximately 20 psi(137 kilopascal) across the entire joint area to squeeze the laminationsout. Heat is applied at temperatures significantly over the meltingpoint of the polyethylene fabric so that the laminations would becomeliquefied and the surface of the woven portions would also becomemelted. The liquefied lamination was then squeezed out from between thefabrics and the melted surfaces of the fabrics themselves were used tomake the joint. Example melting points of some polyethylene fabrics maybe 235 or 265 degrees Fahrenheit (112.8 or 129.4 degrees Celsius). Highand low density polyethylene fabrics are made in the prior art, anddifferent polyethylene fabrics may have different melting points,wherein low density polyethylene generally has a lower melting pointthan high density polyethylene. Temperatures, for example, of 425 to 500degrees Fahrenheit (218.3 to 260 degrees Celsius) are applied in theprior art to melt the laminated film and polyethylene fabric.Additionally, Polyethylene has about 30% less tensile strength thansimilar sized Polypropylene and a great deal greater amount of stretch.Therefore, Polyethylene has not been a useful alternative fabric whenmaking bags to carry the great weights of bulk bags (up to 4,400 pounds(1,996 kilograms) for example).

However, polypropylene is so highly oriented that use of current orstandard heat sealing procedures, which call for temperatures exceedingthe melting point of the fabrics, results in the strength of the fabricitself being immensely deteriorated. Testing conducted with regard todeveloping the present invention has shown an average loss of tensilestrength of approximately 50% when polypropylene fabric is joinedthrough standard heat sealing methods, wherein the fabric is heated to atemperature exceeding the melting point of the fabric. This then resultsin joint strengths that are significantly less than joint strengthscurrently available through sewing polypropylene fabrics. Thickerstronger fabrics may then be preferred to be used so that the finalstrength of a resulting product will safely lift the required weightsnecessary for the product. Further, such joints produced through heatsealing polypropylene fabric with standard heat sealing methods show ameasure of crystallization in the joint area which also reduces theflexibility of the fabrics in the joint areas.

There is a need in the industry to produce products comprisingpolyethylene fabrics with stronger heat sealed seams or joints than whatis achieved by prior art methods of heat sealing polyethylene fabrics.

There is a need in the industry to produce products comprisingpolypropylene fabrics, including fabric bulk bags, by sealing, insteadof stitching the parts or fabric pieces together, given that needlesbreak frequently and sewing requires an operator to replace the needleand repair the stitches that were not properly applied.

There is also a need in the industry to produce products comprisingpolypropylene or polyethylene fabrics, including fabric bulk bags, bysealing, instead of stitching the parts together. Use of sewing machinesfor bulk bag production, for example, involves high amounts of labor,thread contamination will always be a possibility and powders siftingthrough the sewn seams will always be a concern.

While sewing machines might be able to be automated, they have not beenable to run in an automated manner. Threads break as heat builds up andan operator is needed to re-string the machine with new thread. Thesemachines operate at high speeds and often skip stitches. This requiresan operator to see this quality issue and repair it right away.

The following prior art references are incorporated herein by reference.

Patent/ Publication No. Title Issue Date 6,374,579 Liner Bag for Apr.23, 2002 Flexible Bulk Container 6,935,782 Bulk Bag with Aug. 30, 2005Seamless Bottom 8,297,840 Heat Activated Adhesives Oct. 30, 2012 for BagClosures 2008/0115458 Pillow Packaging Bag, May 22, 2008 Pillow TypePackaging Body, Heat Seal Bar for Pillow Packaging Machine, and PillowPackaging Machine 2010/0209025 Flexible Package Bag Aug. 19, 2010Provided with One-Way Functioning Nozzle and Packaging Structure forLiquid Material 2011/0085749 Open Mesh Material Apr. 14, 2011 and BagsMade Therefrom 2011/0206300 Side-Gusset Bag Aug. 25, 2011 2012/0227363Method and Apparatus for Sep. 13, 2012 Top Sealing Woven Bags2012/0314979 Bag and Method of Dec. 13, 2012 Manufacturing a Bag2013/0202231 Composite Film Bag for Aug. 08, 2013 Packaging BulkProducts 2013/0209002 Easy Open Plastic Bags Aug. 15, 2013

BRIEF SUMMARY OF THE INVENTION

The apparatus and method of the present invention solves the problemsconfronted in the art in a simple and straightforward manner What isprovided is an alternative method of connecting woven polypropylenefabrics, or similar fabrics without the use of sewing machines andsewing threads. Also provided is a method for connecting polyethylenefabrics without use of sewing machines and sewing threads. The presentinvention is useful in the production of bulk bags, and will also willapply to any product for which one wishes to connect polypropylenefabrics, polyethylene fabrics, or similar fabrics without the use ofsewing machines. This invention also relates to the ability to produceproducts involving connecting polypropylene fabrics or similar fabrics,including bulk bags, with minimal labor, thereby allowing such productsto be made in all areas of the world where the products are needed,versus only being produced in volume in those areas of the world withlarge amounts of low wage labor.

An object of the present invention is thus to provide an alternative tosewing polypropylene or other similar fabrics in producing bulk bags andother flexible fabric products or containers. The present inventionseeks to provide an alternative method of connecting woven polypropylenefabrics or similar fabrics without the use of sewing machines and sewingthreads. While this invention is useful in the production of bulk bags,it will apply to any product that wishes to connect polypropylenefabrics or similar fabrics without the use of sewing machines. ForExample, the present invention may be also useful with smaller bags (forholding 25 to 100 pounds (11 to 45 kilograms)).

Another object of this invention is to design a sealing system that canutilize simple robots for automation in the construction of flexiblefabric containers.

It is a further object of the present invention that a flexible fabricbag or product made by heat sealing versus sewing will have manyadvantages as follows, Lower wage content, reduced or eliminated sewingthread contamination, new needle holes to allow sifting of product outor moisture and contamination in, a more consistent quality controlledby computerized production rather than being hand made with all theattendant consistency issues such a method creates.

It is a further object of the present invention that the flexible fabricproducts made by heat sealing will have great marketplace appeal forthose companies for whom any thread contamination would jeopardize thequality of their product. Such companies would be in the food orelectronics or medical or pharmaceutical industries. These bags wouldhave no threads to endanger things as there would be no sewing.

It is a further object that the present invention to provide a flexiblefabric product would have great appeal to those companies who areconcerned about sifting of their product through the needle holes leftby the sewing process. Such companies may include the carbon blackcompanies, where very tiny amounts of their product can make very largemesses. Other companies may include companies whose products are goinginto sensitive end user environments where small amounts of theirproducts would contaminate the area.

It is a further object of the present invention to provide a flexiblefabric product that would not require a polyethylene liner. This wouldbe useful for companies who are using polyethylene liners to preventsifting and contamination. Liners make bulk bags, for example, moredifficult to work with and add a notable amount of cost to the overallproduct.

It is a further object that the present invention to provide a methodthat allows companies to pursue full automation for woven fabric productproduction.

It is a further object of the present invention to provide heat sealedjoints with minimal damage of the original fabric for allowing lowercosts through facilitating automated production to reduce labor costs,and also facilitating reduction of fabric weights and thicknesses whileproviding similar overall strengths through higher seam efficiencies.

It is a further objective of the present invention to use heat sealingequipment, which can be automated, to produce polypropylene productswithout requiring stitched seams or sewing machines. It is also anobjective of the present invention to use heat sealing methods toproduce products comprising fabrics similar to polypropylene, withoutrequiring stitched seams or sewing machines.

Another objective of the present invention is to facilitate a robotic orautomated system for production of large fabric bags, for examplepolypropylene bulk bags or barrier cells, for forming a flood barrier,for example, when filled with sand or the like, using robots or otherautomated system.

A further objective of the present invention is to provide a heat sealedpolypropylene product that may be manufactured without human touch onthe inside of the product, so as to maintain a sterile product and helpeliminate a concern regarding bacterial contamination of polypropylenestorage products, as well as to eliminate the possibility of leakagethrough sewing holes, so that the product may be used in medicalapplications, for example in the pharmaceutical industry.

In developing the present invention, testing and experimentation wasconducted. For example, testing and experimentation with heat sealingpolypropylene fabric was conducted. Test results showed that thesefabrics are highly oriented for strength. This high orientation and themolecular structure of polypropylene made efforts to connect two piecesof this material difficult. To join polypropylene pieces of fabricrequired such a level of heat that the polypropylene fabric simplycrystallized making it brittle and not helpful for the purpose oflifting great weights, a purpose for which bulk bags, for example areroutinely used.

Besides crystallizing the fabric, heat sealing polypropylene fabricusing standard procedures known in the art resulted in seams with twodistinctly different strengths. In seaming operations, including whensewing, there exists a “shear strength” and a “peel Strength”. Forexample, the lift loops sewn to the side walls of a bulk bag haveamazing strength when pulled straight up as this motion utilizes theshear strength of this joint, where the entire joint is sharing the loadat all times. But if the bag is lying on its side and it is picked up byone loop, the joint is temporarily put into a position where the peelstrength becomes critical, where one edge of the joint is attacked. Thusin shear strength position, the entire joint is sharing the load at alltimes. In the peel strength position, only one edge of the joint isattacked or bearing the load. As that edge fails, the next edge and thenthe next edge fail in sequence.

This peel versus shear strength issue was considered when experimentingwith heat sealing polypropylene fabric, for constructing bulk bags forexample, because any interior panel that may be installed via heat sealin a bulk bag may be attacked by fill material weight from either side.It is also difficult to control all filling situations in the field. Anobject of the present invention is to create a seam that will work inboth directions. An object of the present invention was also to developdifferent seam configurations that would always have shear strengthworking for it.

When testing panels for inside a fabric container, for flood wall usefor example, an upside down “T” shape seam construction was developedand used. Testing revealed that if the force came from the right side ofthe ‘T’ the right side of the seal or joint would be in shear and theleft side would be in peel. But the right side would protect the leftside with all of its sheer strength. If the load or force came from theleft side the seam would work in reverse with the sheer strength on theleft protecting the peel on the right.

In further testing conducted with polypropylene fabrics, different glueswere tested for making usable joints with polypropylene fabric. Testresults using Super Glue showed that Super glue did not achieve a 20pound (9 kilogram) shear strength.

Testing was also conducted using different types of fabric. Polyethylenefabric is similar to polypropylene but is not as highly oriented andmany products comprising polyethylene have been made using standard heatsealing methods.

Testing and experimentation with polyethylene fabric showed thatpolyethylene fabrics were generally about 30% weaker than polypropylenefabrics. Testing was performed with regard to heat sealing polyethylenefabric to produce a bulk bag. As previously discussed, polypropylenefabric has been preferred in the bulk bag industry given its higherstrength.

The prior art methods of heat sealing generally involve high enough heatand high enough applied pressure to melt the basic fabrics and join themtogether. This method purposefully, melts any applied coating andsqueezes it aside through the high pressure levels so that the basewoven materials can be joined together. This method has been successful,with polyethylene fabrics and was necessary because the strength beingrelied upon came from the woven fabrics. The coatings were generallyapplied for the purpose of providing dust and/or moisture control. Thetechnology at the time for applying the laminations did not providedependably strong attachments of the coating to the fabric itself.Therefore, the art of joining the fabrics intentionally melted away thelaminated materials by melting them and squeezing them out from betweenthe fabrics.

In the prior art, the standard method discussed above has been appliedto woven fabrics that have a thin layer of laminated film on at leastone side, for example a 1 or 2 mil (0.0254 or 0.0508 mm) layer. Forpolyethylene fabrics standard laminated film or coating is oftencomprised of polyethylene, or a mixture of polyethylene and otheradditives. Standard prior art methods apply pressure to squeeze thelaminated film or coating out from between the layers of polyethylenefabric, to allow the fabric pieces to melt and join together.Traditionally in the art, the laminated film or coating was not verysecurely attached to the woven fabrics. Therefore, if the joint includedthe laminated film itself, the lamination became the cause of the jointfailure because of its weak attachment to the woven fabrics.

To determine a joint strength, laminated woven fabrics may be tensiletested before being joined to get a baseline strength of fabric. Forexample, a fabric may break at 200 lbs per inch (3,572 kilograms permeter) in its raw state. Then two pieces of this fabric may be joinedand then pulled to destruction again. A resulting strength, for example,of 160 to 165 pounds per inch (2,857 to 2,946 kilograms/meter) wouldmean that a resulting joint would have lost 17 to 20% of the totalfabric strength as a result of being sealed together. While this jointstrength may be sufficient based on current industry standards, it stillrepresents a significant cost of inefficiency.

In an embodiment of the method of the present invention, the methodprovides a heat fused joint between pieces of polyethylene fabric byjoining the laminations rather than by joining the fabrics. Currentlaminating methods now produce a cling or connection rate between thewoven fabric and the lamination that is very strong and dependable. Byleaving the lamination in place between the fabrics and not joining thefabric pieces, the improved sealing method of the present invention addsthe strength of the lamination to the total strength of the joint.Additionally, since the method of the present invention does not damagethe fabric by melting the woven portions, the sealed joint retainsvirtually all of the base woven fabrics strength. The small percentageof strength lost, for example two or three percent of strength that maybe lost, is the result of minimal damage to the laminated film throughmelting and fusing that occurs in the present method.

In the prior art, pressure may generally be applied at approximately 20psi (137 kilopascal) across the entire joint area to squeeze thelaminations out. Heat is applied at temperatures significantly over themelting point of the polyethylene fabric so that the laminations wouldbecome liquefied and the surface of the woven portions would also becomemelted. The liquefied lamination was then squeezed out from between thefabrics and the melted surfaces of the fabrics themselves were used tomake the joint. Example melting points of some polyethylene fabrics maybe 235 or 265 degrees Fahrenheit (112.8 or 129.4 degrees Celsius). Highand low density polyethylene fabrics are made in the prior art, anddifferent polyethylene fabrics may have different melting points,wherein low density polyethylene generally has a lower melting pointthan high density polyethylene. Temperatures, for example of 425 to 500degrees Fahrenheit (218.3 to 260 degrees Celsius) are applied in theprior art to melt the laminated film and polyethylene fabric.

An embodiment of the method of the present invention comprises joiningpolyethylene fabrics using controlled heat, time and pressure amountsthat leave the base or woven materials unmelted and undamaged yet stillmelting the laminations. The pressure levels are kept light enough toleave the lightly melted lamination in place rather than to purposefullysqueeze it out from between the woven portions of the joint.

Another embodiment of the present invention comprises a method of heatsealing polyethylene fabric comprising joining polyethylene fabricsusing controlled heat, time and pressure amounts that leave the base orwoven materials unmelted and undamaged yet still melting thelaminations.

In another embodiment of the method of heat sealing polyethylene fabric,the pressure levels are kept light enough to leave the lightly meltedlamination in place rather than to purposefully squeeze it out frombetween the woven portions of the joint.

In another embodiment of the method of heat sealing polyethylene fabric,seals provide 90% to 97% joint strengths in the shear direction.

In another embodiment of the method of heat sealing polyethylene fabric,the seal comprises a strength of 92 to 95%.

In another embodiment of the method of heat sealing polyethylene fabricthe seal comprises a strength of 96 to 97%.

In another embodiment of the method of heat sealing polyethylene fabric,the method comprises heating a laminated film or coating on polyethylenefabric pieces right at or barely above the melting point of thepolyethylene fabrics so that only the lamination is melted andliquefied. Then light pressures, for example 5 to 6 psi (34 to 41kilopascals), are used to join the laminations of the fabric piecestogether, rather than to push them away and join the underlying fabrics.In another embodiment of the method of heat sealing polyethylene fabric,the method provides a heat fused polyethylene seal or joint with 90 to97% strength, as compared to the strength of the original fabric.

Another embodiment of the present invention comprises heat fusingpolyethylene fabrics to produce a bulk bag. In an embodiment of thepolyethylene bulk bag of the present invention, the bag would notinclude lift loops but would include fabric tunnels which would use thestrength of the entire bag fabrics for lifting versus the lift loop bagsthat use only a small portion of the fabric for lifting. Testing resultsfor an embodiment of the present invention, showed that a heat sealedbulk bag built out of polyethylene fabric held over 18,000 lbs (8,165kilograms) of hydraulic pressure before failing. On a 5 to 1 safetyratio, this bag could be useful for applications that carry up to 3600lbs (1,633 kilograms). In this embodiment, the method used all of thefabric on two sides of the bag. Further, the fabric was doubled so theheat seal would be on the bottom of the bag and protected from anypotential peeling forces. Although the heat fused polyethylene bag hadnearly 50% more materials, this embodiment of the bag, still eliminateda lot of the labor associated with producing fabric bulk bags via sewingmethods.

In another embodiment of the method of heat sealing polyethylene fabric,impulse heat sealing equipment is used to deliver controlled amounts ofheat for controlled amounts of time to specified portions of the fabricwhich result in a two inch wide seal. In another embodiment of themethod of heat sealing polyethylene fabric, these seals provide 90% to97% joint strengths in the shear direction.

In another embodiment of the method of heat sealing polyethylene fabric,heat sealing equipment may be automated, and sensors can be attached tomonitor time, heat, and pressure. These readings can transfer to a watchstation in a control room. Robots can move the materials from workstation to work station and fabric can be positioned and sealedrobotically.

In another embodiment of the method of heat sealing polyethylene fabric,using relatively low heat and low pressure, only the coating itself isbeing joined. This leaves the fabric completely undamaged andunweakened. In fact, the strength of the coating now adds to the overalljoint strength rather than being squeezed out in the current methods.With the resulting joint strengths, one is now able to lift greaterweights with less material than can be done with the current, commonlyused methods of sewing fabrics together.

When developing an embodiment of a heat sealed polyethylene bulk bag,the following factors were considered. First, there are many changes indirection and different or special shapes for heat sealing equipment maybe needed for production of bulk bags. Second, safety levels forpolyethylene bulk bags would preferably be similar to the safety levelsof polypropylene fabric bulk bags, which are 30% stronger.

When testing an embodiment of a heat sealed polyethylene bulk bag, theresults showed 93% joint efficiency.

In an embodiment of a polyethylene bulk bag of the present invention,the lift loops were eliminated and replaced with fabric tunnels whichwould use the strength of the entire bag fabrics for lifting versus thelift loop bags that use only a small portion of the fabric for lifting.

Experimental models were constructed to identify and evaluate anypractical issues. In one embodiment, test results showed that a heatsealed bulk bag built out of polyethylene fabric held over 18,000 lbs(8,164 kg) of hydraulic pressure before failing. On a 5 to 1 safetyratio, this bag could have been sold for applications that carried up to3,600 lbs (1,632 kg). In this embodiment, the method used all of thefabric on two sides of the bag. Further, the fabric was doubled so theheat seal would be on the bottom of the bag and protected from anypotential peeling forces. This meant that the heat fused polyethlene baghad nearly 50% more materials. This embodiment of the bag, however,still eliminated a lot of the labor associated with producing fabricbulk bags via sewing methods.

An embodiment of the method of the present invention is a method toproduce bulk bags or any flexible fabric container comprisingpolypropylene fabrics in a manner that can result in joints that areheat sealed in such a manner that the natural stresses on each heatsealed joint will be applied to the joint or seam in the sheer directionfor the greatest strength. In the preferred embodiment a method ofproducing poplypropylene bulk bags would utilize a mixture of a minimumof 70% pure VERSIFY™ 3000 (Trademark of The Dow Chemical Company) and25% Polyethylene, and 5% other additives such as pigments or UltraViolet (UV) inhibitors. Other potential additives may includeanti-static protection. Properly sealed, this system will produce heatsealed joints resulting in an average joint strength of 92% of thestrength of standard 5 ounces per square yard (169.53 grams per squaremeter) woven polypropylene.

Another embodiment of the present invention comprises a method ofjoining highly oriented polypropylene woven fabrics by the followingsteps: coating the fabrics with materials, wherein one piece of fabricto be joined is coated with materials comprising VERSIFY™ 3000, whichhas a melting point lower than the polypropylene fabric, and wherein theother piece of fabric to be joined is coated with a standard industrycoating; heating the coating comprising VERSIFY™ 3000 to its lowermelting point; and joining the coatings with pressure light enough toallow the coating to stay in place and generally keep the woven fabricsfrom touching.

In an embodiment of the present invention, the strength of the coatingadds to the overall joint strength, and resulting joint strengths,allows one to lift greater weights with less material than can be donewith the current, commonly used methods of sewing fabrics together.

In another embodiment of the present invention, a coating comprising asuitable percentage of VERSIFY™ 3000, or other suitable propyleneelastomer or plastomer coating with a melting point lower than themelting point of the polypropylene fabrics, will be applied to at leastone side of one piece of polypropylene fabric and a standard industrycoating will be applied to at least one side of another piece ofpolypropylene fabric. Standard industry coatings for polypropylenefabric generally comprise a majority percentage of polypropylene and asmall percentage of polyethylene. The piece of fabric comprising theVERSIFY™ 3000 coating, or other suitable propylene elastomer orplastomer with a melting point below the melting point of thepolypropylene fabric, will be positioned to overlap the piece of fabriccomprising the standard coating, and positioned so that the coatinglayers are in contact. Low heat and low pressure will be applied to meltthe coating and form a joint between the coatings of the polypropylenefabric. This embodiment of the present invention is cost effectivebecause standard coatings cost less than coating comprising VERSIFY™3000, for example. Testing results have shown similar seam strengthswhen joining one fabric comprising a VERSIFY™ 3000 coating and joininganother fabric comprising a standard coating. A notable amount of moneymay be saved as the standard coating is far less expensive. In apreferred embodiment both the VERSIFY™ coating, or other suitablepropylene elastomer or plastomer with a melting point below the meltingpoint of the polypropylene fabrics, and the standard coating will beapplied to a 2.5 mil (0.0635 mm) thickness. In a preferred embodiment ofthe present invention, the coating is applied at a 2.5 mil (0.0635 mm)thickness. Generally in the prior art, standard industry coatings areapplied at 1 mil (0.0254 mm) thickness.

In an embodiment of the method of the present invention, the method isfor creating a new form of heat welding seam for polypropylene fabricsthat provides as high as 95% seam strength in the shear position. Anobjective of the present invention is to use that seaming method tocreate a safely improved bulk bag that is competitive in themarketplace.

Another embodiment of the method of producing flexible fabric bags,comprising the steps of coating a polypropylene fabric with 100%VERSIFY™ 3000 or a combination VERSIFY™ 3000 and polyethylene, andjoining the fabrics (not specifically just edges) using a combination ofheat and minimal pressure in such a manner that the only the coatingsare welded together and not the fabrics. Thus producing a joint thatwill have a strength greater than the original uncoated fabric.

An embodiment of the method of the present invention comprises usingheat to combine the laminated coatings of the fabrics versus trying tocombine the fabrics themselves. Since the coatings have a marginallylower melting point then the fabric itself, this invention joinspolypropylene fabrics without damaging the tensile strength of theoriginal fabrics.

In an embodiment of the present invention, impulse heat sealingequipment is used to deliver controlled amounts of heat for controlledamounts of time to specified portions of the fabric which result in a 2inch (5.08 cm) wide seal. In an embodiment of the present invention,these seals provide 85% to 96% joint strengths in the shear direction.

In an embodiment of the present invention, heat sealing equipment may beautomated, and sensors can be attached to monitor time, heat, andpressure. These readings can transfer to a watch station in a controlroom. Robots can move the materials from work station to work stationand fabric can be positioned and sealed robotically.

An embodiment of the method of the present invention enables productionof a robotically manufactured bulk bag that has very little labor,wherein the bulk bags will not have human touch on the inside of the bagso as to prevent human bacteria contaminations.

An embodiment of the present invention comprises a robotic or automatedsystem for production of large fabric bags, for example polypropylenebulk bags or barrier cells, for forming a flood barrier, for example,when filled with sand or the like using robots or other automatedsystem.

Another embodiment of the present invention comprises a simple roboticor automated system that may fit into a 40 foot export container, orother suitable transportation means, that one could then take to anypotential flood site or project site and start producing 500 footlengths of fabric bags or containers or cells on site, for example. Therobotic or automated system would be similar to a system used to makeendless rain gutters for homes and apartments, for example. In anotherembodiment of the present invention, the automated or robotic systemwould also enable production of other polypropylene or similar fabricproducts on site, in various length measurements as may be suitable fora particular purpose or project.

In another embodiment of the present invention, what is provided is amethod of producing a flexible fabric bags, comprising the steps ofcoating a polypropylene fabric bags with heat fused seams comprising: acombination of VERSIFY™ 3000, or other propylene elastomer or plastomerwith a melting point below the melting point of the polypropylenefabric, and comprising polyethylene; providing fabric pieces, whereineach fabric piece has a coated side and an uncoated side; positioningfabric pieces so that a coated side of one fabric piece faces a coatedside of another fabric piece, selecting an area of fabrics to be joinedfor forming one or more seams or joints and applying heat to the coatedfabric at the joint under a pressure of area to be joined that is lessthan 2 psi (13.8 kilopascal), to form a joint with at least a 90% jointefficiency in a joint tensile test.

Another embodiment of the method of producing flexible fabric bags,comprises the steps of coating a polypropylene fabric with a combinationof VERSIFY™ 3000, or other suitable propylene elastomer or plastomerwith a melting point below the melting point of the polypropylenefabric, and polyethylene; joining edges of the coated fabric, applyingheat to the coated fabric at the joint under a pressure of less than 2psi (13.8 kilopascal), to form a joint with at least a 90% jointefficiency in a joint tensile test.

Another embodiment of the method of producing flexible fabric bags,comprises the steps of coating a polypropylene fabric with 100% VERSIFY™3000, or other suitable propylene elastomer or plastomer with a meltingpoint less than melting point of the polypropylene fabric, or coatingthe fabrics with a combination VERSIFY™ 3000, or other suitablepropylene elastomer or plastomer with a melting point below the meltingpoint of the polypropylene fabric, and polyethylene, and joining thefabrics (not specifically just edges) using a combination of heat andminimal pressure in such a manner that only the coatings are weldedtogether and not the fabrics, thus producing a joint that will have astrength greater than the original uncoated fabric.

In another embodiment of the present invention, all weight bearingpoints in the flexible bag are designed so that the welded joint will bestressed in the sheer direction when the bag is being properly used.

In another embodiment of the present invention, if lifting loops areprovided, the lifting loops are further protected against peel forceswith an additional piece of protective piece of material applied overthe top portion of the lift loop seam to protect against peel pressures.

An embodiment of the present invention comprises a method of producing aflexible polypropylene fabric bags with heat fused seams comprising:providing fabric pieces, wherein each fabric piece has a coated side andan uncoated side; positioning fabric pieces so that a coated side of onefabric piece faces a coated side of another fabric piece; selecting anarea of fabrics to be joined for forming one or more seams or joints;applying heat to the area to be joined that is less than the meltingpoint of the fabrics, for forming one or more seams or joints.

In another embodiment of the method of the present invention, the seamsor joints between pieces of fabric are formed one at time, to produce aflexible polypropylene fabric bulk bag.

In another embodiment of the method of the present invention, the seamsor joints between fabric pieces are joined in a single step to producethe main body of the flexible polypropylene fabric bulk bag.

In another embodiment of the method of the present invention, the seamsor joints of the flexible polypropylene fabric bulk bag retain at least85% of the fabric strength without using sewing machines.

In another embodiment of the method of the present invention, the seamsor joints of the flexible polypropylene fabric bulk bag retain at least90% of the fabric strength.

In another embodiment of the method of the present invention, the seamsor joints of the flexible polypropylene fabric bulk bag retain at least96% of the fabric strength.

In another embodiment of the method of the present invention, retain atleast 100% of the fabric strength without using sewing machines.

In another embodiment of the method of the present invention, for eachseam or joint, a joined coated portion of one fabric piece forms a halfof one seam or joint, and a joined coated portion of another fabricpiece comprises a second half of the same seam or joint.

Another embodiment of the present invention comprises a method ofproducing flexible fabric bags with heat fused seams in a single step,comprising: a. providing 8 layers of flexible fabric, including: i. atop layer for a top panel, having a flat side; ii. a second layer for abody panel, having a flat side; iii. a third layer for a body panel,having a gusset side; iv. a fourth layer for a top panel, having agusset side; v. a fifth layer for a top panel, having a gusset side; vi.a sixth layer for a body panel, having a gusset side; vii. a seventhlayer for a body panel, having a flat side; viii. an eighth layer, for atop Panel having a flat side; b. wherein the layers of fabric comprise alayer of coating; c. positioning the layers of flexible fabric so thatall areas intended to be joined have coating facing coating and allareas intending not to be joined are uncoated fabrics facing uncoatedfabrics; d. positioning the layers of fabric so that there is an overlapof the fabric layers; e. centering the overlapped portions of fabricunder seal bar; and f. applying low heat and low pressure to create heatfusion seams.

In another embodiment, the coated area is substantially coextensive withone side of the fabric portion.

In another embodiment of the method of the present invention, the methodcomprises pulse heating.

In another embodiment of the method of the present invention, heat isapplied from top and bottom directions to the flexible layers of fabric.

In another embodiment of the method of the present invention, heat isapplied from one direction to the flexible layers of fabric.

Another embodiment of the present invention comprises, a polypropylenecontainer comprising heat fused seams, wherein the seams comprise a ‘T”shape, and wherein the right side of the “T” seam in a shear positionenables protection of the left side in a peel position when force isapplied in the right direction, and wherein the left side of the “T”seam in a shear position enables protection of the right side in a peelposition when force is applied in the direction of the left side.

Another embodiment of the present invention comprises a method ofautomated production for producing flexible fabric bags with heat fusedseams comprising: a. providing layers of flexible fabric, includingtubular flexible fabrics, wherein some layers are gusseted and somelayers are flat, and wherein the layers of flexible fabric comprise alayer of coating; b. positioning the layers of tubular flexible fabricso the gusseted layers comprise coating on the outside and the flatfabric layers comprise coating on the inside of their gussets; c.positioning the layers of fabric so that one layer overlaps an adjacentlayer; and d. applying low heat and low pressure to the overlappedportions of the layers of fabric to create heat fusion seams.

Another embodiment of the method of producing flexible fabric bags withheat fused seams comprises: a. providing fabric pieces, wherein eachfabric piece has a coated side and an uncoated side; b. applying heatthat is less than the melting point of the fabric pieces to be joinedfor joining fabric pieces to create one or more seams or joints whereinfor each seam or joint, a coated side of one piece of fabric will form ahalf of the seam and will face a coated side of another piece of fabricfor forming the other half of the seam.

In another embodiment of the present invention, the one or more jointshave a joint strength equal to or greater than 85% of the fabric.

In another embodiment of the present invention, the one or more jointshave a joint strength equal to or greater than 85% of the fabric withoutusing sewing machines.

In another embodiment of the present invention, the overlapped portionsof fabric is 1½ (3.81 cm) inches and the overlapped portions of fabricare centered under a 2 inch (5.08 cm) wide seal bar.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

For a further understanding of the nature, objects, and advantages ofthe present invention, reference should be had to the following detaileddescription, read in conjunction with the following drawings, whereinlike reference numerals denote like elements and wherein:

FIGS. 1-2 are charts showing comparative data from test results on priorart seams for bulk bag construction using standard sewing seam methodson both weft and warp direction yarns of the fabric;

FIG. 3 illustrates a simple sewn seam of the prior art;

FIG. 4 illustrates a pre-hemmed sewn seam of the prior art;

FIG. 5 illustrates a prior art pre-hemmed sewn seam of a bag in a filledposition;

FIG. 6 is a chart showing test results of a fusion heat seam bulk bag ofthe present invention;

FIG. 7 is a perspective view of a bulk bag of the present invention withheat fusion seams;

FIGS. 8-9 are prior art views of a sewn seam bag, and of the sewingprocess of the prior art;

FIG. 10 illustrates the position of a prior art seam as sewn;

FIG. 11 illustrates the position of a prior art sewn seam when a bag isfull;

FIG. 12 illustrates a heat fusion seam of an embodiment of the presentinvention;

FIG. 13 illustrates use of a heat seal bar in an embodiment of the heatfusion seal method of the present invention;

FIG. 14 illustrates a fill or discharge spout of an embodiment of a heatfusion seal bag of the present invention;

FIG. 15 illustrates a top or bottom panel of an embodiment of a heatfusion seal bag of the present invention;

FIG. 16 illustrates a tubular body panel of an embodiment of a heatfusion seal bag of the present invention;

FIG. 17 illustrates an end view of a folded fill or discharge spout ofan embodiment of a heat fusion seal bag of the present invention;

FIG. 18 illustrates an end view of a folded top or bottom panel of anembodiment of a heat fusion seal bag of the present invention;

FIG. 19 illustrates an end view of a folded bag body of an embodiment ofa heat fusion seal bag of the present invention;

FIG. 20 illustrates a side view of a folded top or bottom panel of anembodiment of a heat fusion seal bag of the present invention;

FIG. 21 illustrates an overall view of embodiment of a heat fusionsealed bag of the present invention;

FIG. 22 illustrates layering of fabrics in an embodiment of the heatfusion seal method of the present invention.

FIG. 23 illustrates layering of fabrics in an embodiment of the heatfusion seal method of the present invention.

FIG. 24 illustrates a sample of a heat fusion seam of the presentinvention wherein the fabric of the wall is doubled;

FIG. 25 illustrates an overall view of a fusion heat sealed fabric bagof the present invention; and

FIG. 26 illustrates an isolated view of a heat fusion seal of thepresent invention wherein the edges of the fabric at the point of theseal are overlapped.

DETAILED DESCRIPTION OF THE INVENTION

In the method of the present invention, what is provided is a heatsealing method that does not substantially damage the strength of thepolypropylene fabric yet still gets a final joint strength equal to orexceeding the strength of the current sewing methods. During testing,products produced using the method of the present invention haveachieved joint strengths of 90 to 102% of the strength of thepolypropylene fabrics which is considerably above the joint strengths ofseams achieved through sewing.

In an embodiment of the present invention, the invention will aid andenable the automation of bulk bag production, thus freeing up thelocation of factories around the world. Due to the improved jointstrength, this invention will enable the use of thinner materials toaccomplish the lifting of similar weights.

In an embodiment of the present invention, a suitable coating, forexample VERSIFY™ 3000, a product produced by The Dow Chemical Company isapplied to the polypropylene fabrics or similar fabrics, and provides upto 240 lbs of hold or grip per lineal inch (4,286 kilogram/meter) (tothe polypropylene fabric from a heat seal of 1½ inches (3.81 cm) acrossthe joint area. In another embodiment, a coating, for example VERSIFY™3000, a product produced by The Dow Chemical Company is applied to thepolypropylene fabrics or similar fabrics, and provides up to 200 lbs ofhold or grip per lineal inch (3,572 kilogram/meter). In a preferredembodiment, the coating has a melting point which is lower than themelting point of the fabrics being joined together. The method of heatsealing is an improvement over the known art in the woven fabricsindustry today.

A suitable coating may be a propylene plastomer and elastomer, forexample Versify™ 3000. The coating may contain for example 50% to 90%polypropylene based polymer and 10%-50% polyethylene, by weight.

In a coating to be used in a preferred method of the present inventionfor heat joining polypropylene fabric, one can use 10-99%, preferably20-95%, more preferably 30-95%, and most preferably 75-90% propyleneplastomers, elastomers, or combinations thereof;

one can use 0-5% additives for color, anti-static, or other purposes(these do not materially affect the performance of the coating, and aretypically minimized as they are more expensive than the propylene andpolyethylene);

the balance is preferably polyethylene plastomers, elastomers, orcombinations thereof.

Preferably, the propylene plastomers, elastomers, or combinationsthereof have a density of 0.915 to 0.80 grams per cc, and morepreferably 0.905 to 0.80 grams per cc. Preferably, the polyethyleneplastomers, elastomers, or combinations thereof have a density of 0.91to 0.925 grams per cc. Typically, one should use at least 5% low densitypolyethylene to make the coating run, and preferably at least 10%.

EXAMPLE

In a preferred embodiment of the present invention, the fabrics are onlybeing heated to the melting point of the coating which is lower than themelting point of the fabrics being joined together. In a preferredembodiment of the present invention, the joining temperatures are atleast 5 degrees less than the melting point of the polypropylene fabricsto be joined. Different polypropylene fabrics will have differentmelting points, and in an embodiment of the method of the presentinvention, the joining temperatures are at least 5 degrees less than themelting point of the particular polypropylene fabrics to be joined. Anexample polypropylene fabric may have a melting point of 320 degreesFahrenheit (176.7 degrees Celsius), and thus in an embodiment of thepresent invention, the coating will be heated to 315 degrees Fahrenheit(157.22 degrees Celsius). By using a lower heat than the polypropylenefabrics, the method of the present invention does not damage or reducethe strength of the fabric as typically happens when using the prior arthigh heat formulas for heat welding. Further, in an embodiment of thepresent invention, the clamping pressure used to make the seal isdesigned to be low enough (for example 7 psi (48 kilopascal)) to leavethe coating largely in place and the materials to be joined, largelyseparated by the coatings. Clamping pressures may also be lower, forexample under 2 psi (13.8 kilopascal). Typically in the prior art heatsealing methods, the clamping process is designed to purposefully meltand push aside any coatings on the fabric and join the fabric yarnsdirectly. When any part of the fabric yarns are heated to and past theirmelting point and that is combined with high pressure (for example 20psi (137.9 kilopascal)), the yarns are thinned out, weakened andpartially crystallized.

It is an objective of the present invention to heat fuse fabricstogether. In a preferred embodiment of the present invention, fabricsare not being heated up past their melting points, which is useful inpreventing degradation of the strength of the fabric. In a preferredembodiment of the present invention, the fabrics are only being heatedto the melting point of the coating which is lower than the meltingpoint of the fabrics being joined together. In an embodiment of thepresent invention, the joining temperatures are at least 5 degrees lessthan the melting point of the polypropylene fabrics to be joined.Different polypropylene fabrics will have different melting points, andin an embodiment of the method of the present invention, the joiningtemperatures are at least 5 degrees less than the melting point of thepolypropylene fabrics to be joined. (An example polypropylene fabric mayhave a melting point of 320 degrees Fahrenheit (176.7 degrees Celsius),and thus in an embodiment of the present invention, the coating will beheated to 315 degrees Fahrenheit (157.22 degrees Celsius)). By using alower heat than the polypropylene fabrics, the method of the presentinvention does not damage or reduce the strength of the fabric astypically happens when using the prior art high heat formulas for heatwelding. Further, in an embodiment of the present invention, theclamping pressure used to make the seal is designed to be low enough(for example 7 psi (48 kilopascal)) to leave the coating largely inplace and the materials to be joined, largely separated by the coatings.Clamping pressures may also be lower, for example under 2 psi (13.8kilopascal). Typically in the prior art heat sealing methods, theclamping process of the prior art is designed to purposefully melt andpush aside any coatings on the fabric and join the fabric yarnsdirectly. Naturally, when any part of the fabric yarns are heated to andpast their melting point and that is combined with high pressure (forexample 20 psi (137.9 kilopascal)), the yarns are thinned out, weakenedand partially crystallized.

In the present invention, using low heat and low pressure, only thecoating itself is being joined. This leaves the fabric completelyundamaged and unweakened. In fact, the strength of the coating now canadd to the overall joint strength rather than being squeezed out in thecurrent methods. With the resulting joint strengths, the presentinvention enables lifting of higher weights with less material, than canbe done with the prior art methods of sewing fabrics together.

As previously, discussed, in a preferred embodiment, the coatingmaterials have a melting point lower than the fabrics to be joined. In apreferred embodiment, the coating materials in the process may be anysuitable material or materials which may be used to successfully carryout the process, and could be selected from a range of coatingmaterials. A suitable coating, for example, may be a propylene plastomerand elastomer, for example VERSIFY™ 3000, a product produced by The DowChemical Company. A suitable coating may contain 50% to 90%polypropylene based polymer and 10%-50% polyethylene, by weight.VERSIFY™ is a registered trademark of The Dow Chemical Company forpropylene-ethylene copolymers used as raw materials in the manufactureof films, fibers and a wide variety of molded plastic objects;propylene-ethylene copolymers used as raw materials in the manufactureof compounds to make coated fabrics, artificial leather, soft touchgrips, shoe stiffeners and flexible roofing membranes.

In a preferred embodiment of the present invention, the method wouldutilize a mixture of a minimum of 70% pure VERSIFY™ 3000 and 25%Polyethylene and 5% of additives such as UV protection and colors. Using100% pure VERSIFY™ 3000, the method of the present invention achieved upto 96% to 102% joint efficiency in a shear joint tensile test, while at70% VERSIFY™ 3000, 91% to 95% joint efficiency has been obtained in thesame test. (The resulting percentages are based on the average strengthof the fabric tested. There is generally approximately a 5% variablestrength in any section of fabric tested.)

Turning now to the figures, the charts shown in FIGS. 1-2, illustratecomparative data and results from testing performed on seams made forbulk bag construction using both the standard sewing seam methods onboth weft and warp direction yarns of the fabric. They are several waysto make prior art seams in the bulk bag industry. In FIGS. 3-4, the mostcommon seams are depicted.

FIG. 3 depicts a simple sewn seam. In FIG. 3, fabric 13 is shown, withsewing stich seam 11, and fabric fold 15, wherein fabric is folded backon itself to create a seam. As shown, the simple seam is just a foldingback of the two pieces of fabric to be stitched together. This simpleseam prevents the interlocking weave from simply slipping off the edgeof the fabric under the extreme pressures that are often found in bulkbag usage. This seam generally creates about a 58% joint strength.

FIG. 4 depicts a pre-hemmed seam, which is created by not only foldingthe fabric back prior to making the joint, but by sewing the folded backportion of the fabric to itself. FIG. 4 shows fabric 13 with sewingstitch seam 11 and stitch to hold the hem 12, wherein the folded backportion is sewn to the fabric itself. This extra step generally createsa seam with an average strength of 63%. 63% over 58% is a strengthincrease of 8.5%. Even though there is extra labor to hem the fabrics, astrength increase gain of this size is often considered important in theindustry.

After the bag is made and filled, the pre-hemmed seam will be in theposition shown in FIG. 5. FIG. 5 depicts heat seal joint 14. This meansthat the majority of the time, the seam is basically in a peel positionwhose strength is largely determined by the strength of the thread beingused. But when seams are able to withstand forces only equal to 63% ofthe fabrics, then the fabrics must be overbuilt to take into account theseam's inefficiency.

When labor is taken into account as well, it is easily seen that thesewing operation is a very large factor in determining the final cost ofmaking bulk bags.

Taking the same fabrics, and using the fusion heat seal seam method ofthe present invention, the graph shown in FIG. 6 shows that the seamstrengths achieved, over 4 sets of tests, averaged 95.75% strengthretention. This is a significant increase of strength retention withthese fabrics.

When 95% of the original strength is being maintained through the fabricconnections, equal fabrics may be used to carry heavier loads, or lessfabric can be used to carry the same load. An embodiment of the presentinvention thus may provide a 50% gain in strength over the sewn seams.

The fusion heat seal seam not only creates a stronger seal, but it doesit in a significantly different manner. The fusion heat seal seam of thepresent invention enables new bulk bag designs that will be able fillthe needs of the bulk bag industry.

In the prior art, due to the nature of sewing machines and the size ofbulk bags, the vast majority of seams must be sewn in an edge to edgepeel position. The throat of a sewing machine is not big enough toeasily allow an entire bulk bag to pass through the throat of themachine. Therefore, sewing is typically designed to place all seams inan edge to edge position as shown in FIG. 9. FIG. 7 depicts a fusionheat seal seam 16 of the fusion heat seal bag 10. FIG. 8 illustrates aprior art sewn seam 11.

Once a sewn seam prior art bag is made and filled, the sewn seam then isput into a peel position that depends entirely on the strength of thecombination of the thread and needle punctured fabrics.

In FIG. 10, you can see the positions of the fabric as it was stitchedby the machine above in FIG. 9. Stitch seam 11 is shown stitchingtogether bag sidewall 17 and bag bottom wall 18. Fabric folds 15 arepositioned so that fabric fold 15 of sidewall 17 is in contact withfabric fold 15 of bottom wall 18. In FIG. 11, the position of the stitchand fabric when the bag is in use are shown. Sewn stitch 11 and joint 14are shown, wherein sidewall 17 and bottom wall 18 are attached. Thefabric folds 15 of each wall 17, 18 are shown in an interior of the bag.Typically, a minimal fabric fold 15 will be 2 inches (5.08 cm) in depthon each side. This means the average sewn seam has 4 inches (10.16 cm)of doubled fabrics.

The fusion heat seal seam of the present invention is formed byover-lapping the fabrics to give the seal a wide shear area forstrength. In an embodiment of the present invention, the fusion seamwill get 95% of the original fabric strength. In a preferred embodiment,there will be an overlap of 1½ to 2 inches (3.81 cm to 5.08 cm). Thissaves a minimum of 2 inches (5.08 cm) of fabric in every joint as theprior art sewn method has 2 inches of doubled fabric layers on bothsides of the seam.

FIG. 12 depicts a fusion heat seal seam of the present invention. InFIG. 12, fabric 13 is shown as a dark line. Coating or lamination 19 ofthe fabrics is shown as a dotted line. Line 20 depicts the sealed orjoined area of fabric, which may be 1½ to 2 inches (3.81 cm to 5.08 cm).

In an embodiment of the present invention the width of the overlap canbe much smaller, for example 0.5 inches (1.25 cm) to save even morefabrics.

It is preferable, that the seams be sealed in a manner that no graspableedge be left on any exterior seams of the bag. This will discourage anyattempt to rip the seal open in the peel position which is the weakdirection of the fusion joint.

In an embodiment of the present invention, the preferred method is tooverlap the fabrics only 1½ inches (3.81 cm) and center this under a 2inch (1.25 cm) wide, for example, seal bar 21 as shown in FIG. 13. InFIG. 13, line 20 depicts the sealed area, which may be 1½ inches (3.81cm) wide. This intentionally leaves a ¼ inch (0.64 cm) gap ortransitional area, represented by arrow 22, on either side of the jointor sealed area 20. This insures that the ending edges of the two halvesof the seal are sealed to the very edge. This leaves no graspable edgeto create an easily peelable area.

The ¼ inch (0.64 cm) transitional area is small enough to preventdamaging heat from overcoming the smaller material volume of the singlelayer and allows for some small misplacement of the fabric edge lineup.

In an embodiment of the method of the present invention, a pulse heatprocess is used. By using impulse heat, the top temperature can becontrolled and held to a desired amount of heat for a desired amount oftime. This then allows the process to bring the material temperatures upto the desired level without going so high as to damage the fabrics butto also hold it there long enough to allow a thorough and even heatingof the joint area.

It is, also, useful to the process to keep equal amounts of materialsunder the seal at all times. The impulse heat process is injecting equalheat throughout the sealing process. If an uneven amount of materialsunder the seal bar is too diverse, then areas with less materials mayabsorb more heat than desired and material damage can occur.

In FIG. 12, with only a single seal being made, the amount of heatapplied is minimal enough that the ¼ inch (0.64 cm) transitional area orgap 22 allows enough heat dissipation to provide a very good sealwithout damage to surrounding materials.

An embodiment of the present invention involves stacking this processand creating multiple seals simultaneously. When stacking the process,placement of materials should be considered and keeping material amountsequal throughout will enable safe repeatability of the sealing process.

What has been described and shown so far is the difference betweensewing seams and heat sealing to make a simple seam using polypropylenefabrics. Hereafter, the construction of bulk bags, that may routinelycarry one ton of dry flowable materials, for example, will be discussed.

An objective of the present invention is to find ways to reduce the costof making a product commonly called by several names. These namesinclude bulk bags, Flexible Intermediate Bulk Containers, FIBC's, BigBags or even Super Sacks (a trademark name of B.A.G. Corporation).Herein the product has been and will be referred to mostly as bulk bags.

The present invention has useful applications with bulk bag production,and is also useful to a number of other packages or products, forexample smaller bags used to carry 25 to 100 pounds (11 to 45kilograms). Other products that will benefit from the present inventioninclude products stored or transported in flexible fabric packaging,wherein a sterile and air tight package is preferred.

Current bulk bag technology, using sewing machines typically travelsstitch by stitch around every inch (centimeter) of seam on every part ofthe bag on an individual basis. In an embodiment of the presentinvention, the invention will simplify this process to create aproductive system that can seal or join the fill spout to the top sheet,the top sheet to the bag body, the bottom sheet to the bag body, and thebottom discharge spout to the bottom sheet in a single moment or step.This eliminates a tremendous amount of labor and time.

Further, in an embodiment of the present invention each heat sealed seammay be approximately 50% stronger than the sewn seam. Because each jointrequires less fabric than the sewn seam, the present invention enablesproduction of a fabric bag that is demonstrably less expensive and moreeconomical to make.

Use of heat sealing is known in the art. No matter what the shape of theseal to be made is, heat bars can be shaped to accomplish that seal andthat shape. In an embodiment of the present invention, a square formedheat bar and structures to hold the fabric in place to allow the joiningof the bottom of the bag to the sidewalls will be used to make a joint.Such equipment, however, may be large, bulky and expensive. Additionalsteps to complete the product and machines may be needed.

In an embodiment of the present invention, the method comprises usingthe fusion heat sealing method of the present invention for productionof bulk bags, wherein individual joints are sealed sequentially, oneafter another. In another embodiment of the present invention, fewersteps and machines are used in fusion heat sealing a bulk bag. Anobjective of the present invention, is to simplify the number of stepswhen producing a bulk bag, as compared to prior art sewing methods.

There are many prior art designs in the bulk bag market but most ofthese designs fall into two basic categories. The body of the bag may bemade from numerous pieces of flat panels sewn together or the body ofthe bag may be made from a single piece of tubular fabric that has novertical seams.

All of the basic designs can be made using the system of the presentinvention. A preferred embodiment of the present invention will startwith a tubular woven body.

Many bulk bags have a fill spout, a top panel, a circular woven bodypanel, a bottom panel and a discharge spout. The two spouts can be madewith tubular fabric with no seams. The body of the bag may be made astubular fabric with no seams. The top and bottom panels are generallysquare flat panels with a hole cut into them to accommodate the spoutsthat must be attached to them. FIG. 14 depicts a fill or discharge spout23. Line 24 represents, for example, a 22 inch width for a (55.88 cm)spout tube, lying flat. Line 25 represents, for example, a 18 inch(45.72 cm) long fill or discharge spout.

FIG. 15 depicts example top or bottom panels 26. In FIG. 15, the top orbottom panel 26 is relatively square with sides being 41 inches (104.14cm) for example, as represented by lines 29. Area 30 represents aconnection area for the fill or discharge spout, with lines 28 being 11inches (27.94 cm) for example.

FIG. 16 depicts a tubular fabric 27, without seams. Line 31 mayrepresent a 45 inch (114.30 cm) height, for example, and line 32 mayrepresent a 74 inch (187.96 cm) width, when the tubular fabric is lyingflat.

Thus, FIGS. 14-16 depict five potential pieces of fabric, a fill spout13, a discharge spout 13, a top panel 23, a bottom panel 23, and atubular fabric piece 26.

In an embodiment of the present invention, a bulk bag may be produced,using fusion heat seal process, in a single step. In a preferredembodiment, the fabric pieces will be gusseted and placed in positionfor the heat fusion sealing process. The FIGS. 17-20 depict the finalform of the fabrics in a preferred embodiment, just prior to making thebasic bag.

In a preferred embodiment the coating side of the fabrics is on theoutside of the tubes and on the inside of the flat panels, so that thecoatings will be facing each other when the bag is formed.

These coating positions can be reversed and put inside of the tubes andoutside of the flat panels for top and bottom, but since coatingnaturally comes on the outside of tubular fabric, the preferred methodis the one shown in the drawings.

FIGS. 17-19 depict folding the bulk bag parts prior to heat sealing in asingle step. As shown in FIGS. 17-19, the folded shape of every piece isbasically the same shape. FIG. 17 depicts an end view of folded fill ordischarge spouts 23, wherein the coating or lamination 19 is on theoutside. Line 33 depicts an 11 inch (27.94 cm) width area, for example.FIG. 18 illustrates an end view of top or bottom panels 26 wherein thecoating or lamination 19 is on the inside. Line 45 depicts a 41 inch(104.14 cm) area, for example. FIG. 19 illustrates an end view of afolded tubular bag body 27 wherein the coating or lamination 19 is onthe outside. Line 46 depicts a 37 inch (93.98 cm) area. FIG. 20 depictsa side view of a folded top and bottom, wherein coating 19 is on theinside. Dotted line 34 represents a future fold line. Corner slits 35are also shown. Approximately a 45 degree angle may be formed.

The folding arrangement as described above, enables each piece to fitinside or around the piece it will be connected to in the productionprocess.

Once the shapes are put together, the bag is ready to seal as shown inFIG. 21. At each of the four fusion heat seal areas or joints 41, theparts are positioned with the outer part having the coating 19 facinginward and the inner part having the coating 19 facing outward as shownin FIGS. 22-23.

This results in a total of 8 layers of fabric at all points from bottomto top. In FIGS. 22-23, layers 1-8 are shown.

Example; Connection of Top to Body of Bag

1. Top layer Top Panel flat side 2. Second layer Body Panel flat side 3.Third Layer Body Panel Gusset side 4. Fourth layer Top Panel Gusset Side5. Fifth layer Top Panel Gusset Side 6. Sixth Layer Body Panel GussetSide 7. Seventh Layer Body Panel Flat Side 8. Eighth Layer Top PanelFlat Side

By lining up multiple layers in this fashion, heat fusion method of thepresent invention is able to completely join the top to the body panelin a single action. When the structure as depicted in FIGS. 22-23 iscollapsed, the structure is always coating 19 to coating 19 for jointcreation and fabric 13 to fabric 13 for not creating a joint. In thedrawings the gussets may be positioned so as to fit together and duringproduction, fabrics are collapsed to a flat condition.

All four joints are made in the same manner.

The method of the present invention using impulse sealing to make jointsthrough multiple layers without exceeding the safe temperature limit,comprises controlled heating that will not rise above the desired levelwhich is less than the melting point of the polypropylene fabric.

In a preferred embodiment, in order to get the entire group of intendedjoints to the right temperature level without damaging the fabricstrength, time will be employed to allow the required heat to becomeuniversal throughout the 8 layers of materials.

Further, it will be useful if the heat mechanisms are mirrored on thetop and bottom so that heat may need to travel only 50% of the totalthickness. This process may also be achievable with one heating elementby using a greater time for the heat to travel throughout the entirestack of fabrics. A preferred method uses heating elements on both topand bottom of the stack.

In an embodiment of the present invention, a single machine with 4heating elements on top and four heating elements on the bottom caneffectively seal, in a single action, all four of the joints shown inFIG. 21 of the complete bag.

The fabrics can be placed and positioned under the sealing mechanisms sothat the heat sealing bars cover the area to be joined plus a ¼ inch(0.64 cm) overlap, for example, to enable sealing of all edges and toalso make them ungraspable. In an embodiment of the present invention,the mechanisms can control heat, time and pressure. When this is done,the bags can be put together in a completely repeatable and dependablefashion with this stage of production requiring a single automatablemachine.

When making bulk bags in this manner, different sizes of bags can bemade by simply changing the length of the body panel. This would requireonly the movement of two heating elements to match the new distancebetween the top and bottom panel attachments. The relationship ordistance between the spout joints and the top and bottom panel would beunchanged.

The method of the present invention may also be used to create differentdesigns of bulk bags, for example baffle bags or bags with liftingloops, with heat fused seals or joints.

This system eliminates the need for threads and the resultingcontamination that often occurs when a cut piece of thread is leftinside the bag. It reduces contamination from sewing machines cominginto contact with various parts of the bag. It reduces human contactwith the inner surfaces of the bag.

Since the seams are solid without any needle holes, this systemeliminates any need for sift-proofing that is often required forstitched bulk bags. The method of the present invention provides a bagthat is nearly air tight.

Due to the airtightness and the cleanliness, it is perceived that thisproduction system may eliminate the need for polyethylene liners thatare often added to the inside of the bulk bag for cleanliness and/ormoisture control. This will reduce the amount of plastic used in theindustry and therefore reduce the amount of materials eventually goinginto landfill.

Notably all four of the seams shown in the preferred embodiment put thefinal seams in the sheer position to withstand the forces of the heavyweights that bulk bags carry. Further, the act of carrying the weightwill always stress these seams in only the shear position.

Thus, in the method of the present invention for automating productionof flexible bags, packages or containers, it should be understood thatthis method would cover all kinds of flexible bags, packages orcontainers.

As previously discussed, the bulk bag industry uses a highly orientedwoven polypropylene fabric. This is based on a cost versus strengthmatrix. Polypropylene has historically been lower in cost per pound(kilogram) and historically stronger than similar polyethylene by about30% in tensile strength. While it was always possible to use a thickerpolyethylene material to make bulk bags, there has been limited interestin using that material due to the ensuing cost of getting the neededstrength. Further, polyethylene fabrics have a lower melting point thanpolypropylene fabrics so once again, polypropylene has been a preferredmaterial for nearly 40 years in this industry. Polypropylene is also avery inert material. It is unaffected by almost every chemical. Thisalso makes it a good choice for making packaging bags. With all of thesebenefits for the industry, one area where polypropylene falls short ofpolyethylene, has been the result of polypropylene's inertness and itsstrength due to high levels of orientation.

Because of this inertness, the entire industry has relied upon aphysical connection of materials for the container construction. It hasrelied nearly 100% on sewing as the method of construction.

One of the common alternate methods of connection to sewing that isautomatable has been to use heat to form joints. When PE fabrics areused, this is very common. But polypropylene crystallizes at the levelof heat needed to form a joint. This crystallization destroys the jointstrength rendering this method previously unusable. There are currentlyno known methods of heat sealing polypropylene fabrics together thatcreate usable seams for the construction of polypropylene bags such asbulk bags.

As stated earlier, the sewing process is very labor intensive and verypoorly suited for any form of automation. Sewing machines have very highspeed parts moving to allow sewing stitches to be applied at thousandsof stitches per minute. At these speeds, even if the machines wereoperated robotically, needles and threads are continually breaking andneeding human repair to be put back into operation. Therefore, due tothe inability to run without constant human support, the bulk bagindustry has never been able to automate its production in an efficientand cost effective manner. This has led to the loss of all of these jobsto overseas plants located in low labor cost countries.

Therefore, there is a need for an automatable system of bag constructionthat will reduce the high levels of labor currently required in theconstruction of bulk bags. This will allow the production to bepositioned close to the end users and eliminate the extremely long leadtimes and high inventory needs that the industry suffers with under thecurrent sewing construction methods.

An embodiment of the method of this invention comprises a method ofconstructing woven fabric bags using a new and unique heat sealingmethod. Use of a heat sealing process is well known and quite common inthe joining of woven polyethylene fabrics. It is commonly understoodthat a joint efficiency of 80% to 85% is an extremely good jointefficiency level. Many operations accept much lower joint efficienciesthat range down into the 70's of the percentage of efficiencies.

In the sewn seams, the efficiency is often only 65%. The strength of thepolypropylene fabric takes these joint efficiencies into considerationwhen choosing the strength of the fabric that will be used in theconstruction of the final container.

Current methods of heat sealing usually involve high enough heat andhigh enough applied pressure to melt the basic fabrics and join themtogether. This method purposefully, melts any applied coating andsqueezes it aside through the high pressure levels so that the basewoven materials can be joined together. This method has been successful,with polyethylene fabrics for example, for several decades. It wasnecessary because the strength being relied upon came from the wovenfabrics. The coatings that were generally applied, were applied for thepurpose of providing dust and/or moisture control.

Because polypropylene is so inert, the coatings being applied had lowattachment strength to the woven fabrics. Therefore, if they were to beused as the attachment point by welding the applied coatings together,the resulting strength would have no real relationship to the strengthof the fabric. The resulting joint strength would only be related to thestrength of the coating's attachment to the woven fabrics. Whenconducting testing with regard to the present invention, of makingjoints that relied on the strength of the coating's attachment using thepresent technology, results showed about a 27% joint efficiency on theparticular strength of materials tested. In these tests, it was neverthe fabric that broke. It was always the coating detaching from thefabric that caused the joint to fail.

In the present invention, a coating that can be applied in a standardextrusion coating method attaches so completely to the polypropylenefabrics that it is no longer necessary to apply high pressure that willsqueeze the coating out from under the heated jaws of the sealingmechanism. In fact, by sealing under less than 10 psi (68.9 kilopascal),it is an objective of this invention to utilize the strength of theapplied coating as part of the strength of the final heat seal. Thefabric itself is nearly undamaged during this heat sealing method. In anembodiment of the present invention, only the coating is intended to bemelted to create the joint. Tests results show achievement of over 90%joint strengths. Some tests results are running up as high as 100% ofthe strength of the coated materials that have not been sealed. However,the resulting strength of the joints many times exceeds the strength ofthe original fabric itself prior to it having been coated.

Therefore in an embodiment of the method of the present invention, themethod of heat sealing creates seams that are sometimes actuallystronger than the original fabric before any process begins. Consideringthat the current methods are working with sewn seams that have a 65%joint efficiency, it is an objective of the present invention that thisheat sealing method will makes heat joints with minimal damage to theoriginal fabric and will allow not only lower costs through automationto reduce labor costs, but will provide many opportunities to reducefabric weights and thicknesses while providing similar overall strengthsthrough the higher seam efficiencies. An example would be as follows; ifthe sewn fabric had a tensile strength of 200 pounds per inch (3,572kilograms/meter), after being sewn the seam would have a strength of 65%of the 200 pounds per inch (3,572 kilograms/meter) or only 130 pounds(58 kilograms). With a 90% joint efficiency, a fabric that had anoriginal strength of 150 pounds per inch (2,678 kilograms/meter) wouldstill create a seam strength of 135 pounds per inch (2,410kilograms/meter). This would allow a 25% reduction in the strength ofthe fabric to create an equal seam. This obviously then will lead tolong term reductions on the amount of fabrics needed with this system tocreate bags with similar strengths.

All seams have at least two measurements that are critical to itssuccess. These are generally called shear and peel tests.

In the shear tests, the joint is made with two ends of the materialbeing joined at opposite ends of the joint area. When the free ends ofthe materials are pulled in opposite directions, the entire sealed areasupports the joint efficiently. This results in the highest possibledemonstration of the sealed joint efficiency.

In the peel test, two free ends of the test materials are on the sameside of the joint. In this case, when the two free ends are pulledapart, only one edge of the seal is stressed at any one time. Thisresults in the peeling of the joint as the ends are pulled apart. Thistypically results in the lowest joint efficiency.

An embodiment of the present invention is illustrated in FIGS. 24-26.FIG. 24, depicts a joint wherein the fabric wall is doubled, in anupside down “T” shape construction. As the fabric meets the end wall,one leg goes to each side, and pressure from either side protects theopposite side with its shear strength. In FIG. 25, a fusion heat sealedbulk bag 10 can be designed in a manner such that lap seams as shown canbe used. The product will always be pushing the joint in the sheardirection, as illustrated by arrows 44 in FIG. 26, which depict pressurebeing applied from product held within a bag.

PARTS LIST PART NUMBER DESCRIPTION  1 layer  2 layer  3 layer  4 layer 5 layer  6 layer  7 layer  8 layer 10 heat Fusion Seam Bulk Bag 11stich seam 12 stich to hold hem 13 fabric 14 sewn joint 15 fabric fold16 fusion heat sealed seam 17 side wall 18 bottom wall 19coating/lamination 20 line 21 heat seal bar 22 transitional gap 23fill/discharge spout 24 line 25 line 26 top/bottom panel 27 body 28 sewnseam 29 line 30 area 31 line 32 line 33 line 34 future fold line 35corner slit 36 gusseted fill spout 37 gusseted top panel 38 gussetedbody 39 gusseted bottom panel 40 gusseted discharge spout 41 fusion sealarea 42 double fabric wall 43 lap seam 44 pressure from bag contents 45line 46 line

All measurements disclosed herein are at standard temperature andpressure, at sea level on Earth, unless indicated otherwise. Allmaterials used or intended to be used in a human being arebiocompatible, unless indicated otherwise.

The foregoing embodiments are presented by way of example only; thescope of the present invention is to be limited only by the followingclaims.

The invention claimed is:
 1. A method of forming a flexible plasticfabric bulk bag with heat sealed joints, comprising the steps of: a)providing a first folded bag portion having a first pair of outer leftedges and a first pair of outer right edges, each of the first pair ofouter left edges being a fold wherein a first left side panel of thefirst folded bag portion is drawn inward and each of the first pair ofouter right edges being a fold wherein a first right side panel of thefirst folded bag portion is drawn inward; b) providing a second foldedbag portion having a second pair of outer left edges and a second pairof outer right edges, each of the second pair of outer left edges beinga fold wherein a second left side panel of the second folded bag portionis drawn inward and each of the second pair of outer right edges being afold wherein a second right side panel of the second folded bag portionis drawn inward; c) overlapping the first and second folded bag portionsto define an overlapped area, wherein in the overlapped area interiorsurfaces of the first folded bag portion are in contact with exteriorsurfaces of the second folded bag portion, and wherein exterior surfacesof the first folded bag portion are in contact with one another, andinterior surfaces of the second folded bag portion are in contact withone another; (d) applying heat and pressure to the overlapped area toform a heat sealed bag joint between the interior surfaces of the firstfolded bag portion and exterior surfaces of the second folded bagportion that are in contact; and wherein the bag joint is not formedbetween at least some exterior surfaces of the first folded bag portionthat are in contact with other exterior surfaces of the first folded bagportion and under the heat and pressure and the bag joint is not formedbetween at least some interior surfaces of the second folded bag portionthat are in contact with other interior surfaces of the second foldedbag portion and under the heat and pressure so that the bulk bag canexpand to an open configuration when filled with bulk material.
 2. Themethod of claim 1 wherein the flexible plastic fabric is polypropylene.3. The method of claim 1 wherein the flexible plastic fabric ispolyethylene.
 4. The method of claim 1 wherein the bag joint is formedbetween an interior surface coating of the first folded bag portion andan exterior surface coating of the second folded bag portion.
 5. Themethod of claim 4 wherein the interior surface coating is different fromthe exterior surface coating.
 6. The method of claim 4 wherein the firstfolded bag portion is a bottom portion and the second folded bag portionis a body portion.
 7. The method of claim 4 wherein the heat sealed bagjoint is a bottom load bearing joint.
 8. The method of claim 1 whereinthe first folded bag portion is a top portion and the second folded bagportion is a body portion.
 9. The method of claim 1 wherein the firstfolded bag portion is a top portion and the second folded bag portion isa top spout.
 10. The method of claim 1 wherein the first folded bagportion is a bottom portion and the second folded bag portion is adischarge tube.
 11. The method of claim 1 wherein the bulk bag can hold2,000 to 4,400 pounds of bulk material.
 12. The method of claim 1wherein the bag joint retains at least 85% to 100% of the fabricstrength.
 13. The method of claim 1 wherein the folded first bag portionis a top portion and the folded second bag portion is a body portion.14. The method of claim 1 wherein the bulk bag can hold 2,000 to 4,400pounds of bulk material.
 15. The method of claim 1 wherein the bag jointretains at least 85% to 100% of the fabric strength.
 16. A method offorming a flexible plastic fabric bulk bag, comprising the steps of: a)providing a folded first bag portion having a first open end; b)providing a folded second bag portion having a second open end; c)overlapping the first and second open ends to put interior surfaces ofthe folded first bag portion in contact with exterior surfaces of thefolded second bag portion to define an overlapped folded first bagportion and an overlapped folded second bag portion in an overlappedconfiguration, and wherein in the overlapped configuration, there are apair of outer left edges and a pair of outer right edges, each of thepair of outer left edges being a fold wherein a left side panel of thefolded first bag portion and a left side panel of the folded second bagportion are drawn inward, and each of the pair of outer right edgesbeing a fold wherein a right side panel of the folded first bag portionand a right side panel of the folded second bag portion are drawninward; d) applying heat and pressure to the overlapped folded first bagportion and the overlapped folded second bag portion in the overlappedconfiguration to form a heat sealed bag joint between the interiorsurfaces of the folded first bag portion and the exterior surfaces ofthe folded second bag portion that are in contact; and e) wherein thebag joint is not formed between at least a substantial portion ofsurfaces of the folded first bag portion that were in contact with eachother when exposed to the heat and pressure and the bag joint is notformed between at least a substantial portion of surfaces of the foldedsecond bag portion that were in contact with each other when exposed tothe heat and pressure, so that the bulk bag can expand to an openconfiguration after the bag joint.
 17. The method of claim 16 whereinthe bag joint is formed between an interior surface coating of thefolded first bag portion and an exterior surface coating of the foldedsecond bag portion.
 18. The method of claim 17 wherein the interiorsurface coating is different from the exterior surface coating.
 19. Themethod of claim 17 wherein the folded first bag portion is a bottomportion and the folded second bag portion is a body portion.
 20. Amethod of forming a heat sealed bulk bag of the type that can hold 2,000to 4,400 pounds of bulk material, comprising the following steps: (a)providing a first folded bag portion having a first heat seal area witha first coating on at least exterior surfaces of the first heat sealarea; (b) providing a second folded bag portion having a second heatseal area with a second coating that is different from the first coatingon at least interior surfaces of the second heat seal area; (c)overlapping the first and second folded bag portions to define anoverlapped area, wherein in the overlapped area the interior surfaces ofthe second heat seal area of the second folded bag portion are incontact with the exterior surfaces of the first heat seal area of thefirst folded bag portion such that the first coating and the secondcoating are in contact, and wherein some exterior surfaces of the secondfolded bag portion are in contact with one another, and some interiorsurfaces of the first folded bag portion are in contact with oneanother; and (d) applying heat and pressure to the overlapped area tocause heat sealing between the first coating and the second coating thatare in contact and form a heat sealed bag joint that has the followingdirectly adjacent layers: (i) first folded bag portion fabric, (ii)first coating, (iii) second coating, (iv) second folded bag portionfabric; and wherein, despite being exposed to the heat and pressure, thebag joint is not formed between the some exterior surfaces of the secondfolded bag portion that are in contact and the bag joint is not formedbetween the some interior surfaces of the first folded bag portion thatare in contact, so that when heat sealing of the bag joint is completedthe bulk bag is expandable to an open configuration.